A Revised Structure for (−)-Dihydropertusaric Acid, a γ-Butyrolactone Acid from the Lichen Punctelia microsticta

Abstract

The gamma-butyrolactone acid (1) and two known compounds, (-)-isomuronic acid and the tridepside gyrophoric acid, have been isolated from the lichen Punctelia microsticta. The structure and stereochemistry of compound 1 were determined on the basis of spectroscopic evidence and molecular modeling. Spectroscopic and physical data of 1 and (-)-dihydropertusaric acid, previously isolated from the lichen Pertusaria albescens, showed that both are the same compound, although for the latter the epimeric structure 2 has been proposed.

Synthesis of (±)-Nephromopsinic, (−)-Phaseolinic, and (−)-Dihydropertusaric Acids

“…The physical and spectral data of 2 are identical to those reported for the (À)-dihydropertusaric acid isolated from the lychen Punctelia microsticta [15] and Punctelia albescens [14]. This total synthesis confirms the recently revised relative and absolute configurations of (À)-dihydropertusaric acid [16]. For the synthesis of (À)-phaseolinic acid (3), the reaction sequence had to be reversed due to problem to purify the methylated lactone.…”

Applications of Transition‐Metal‐Catalyzed Asymmetric Allylic Substitution in Total Synthesis of Natural Products: An Update

“…Structurally, they possess a functionalized tetracyclic skeleton, which features a hydrocarbazole motif with a crucial all-carbon quaternary stereogenic center. In 2013, Shao et al demonstrated the feasibility of divergent total syntheses of (À )-aspidosperma (162) and related natural product (163), (+)-Kopsia, in a concise and divergent manner using Pd-catalyzed DAAS of heterocyclic carbazolones for the first time, which resulted in the formation of highly functionalized chiral carbazolones, featuring an α-quaternary carbon center. The concise enantioselective total synthesis of 162 and 163 was successfully achieved from a common tetracyclic intermediate 166, which was, in turn, prepared from compound 165 in several steps.…”

“…Reduction of the ketone moiety of 205 gave (À )-aspewentin A (204) in 85 % yield, which was then subjected to oxidation of the phenol, yielding (À )-aspewentin C (206) in 13 % yield (Scheme 40). [161] The total synthesis of two members of the paraconic acid [162] family of natural products, so-called (À )-nephroster-anic acid [163] and (À )-roccellaric acid [164] was achieved using the Pd-catalyzed DAAS reaction to allyl dienol carbonate [165] as a crucial step. This aforementioned crucial step also showed several advantages such as being operationally facile, significantly flexible, and most importantly its regioselectivity seems to be highly substrate-dependent, thus has been used in some other organic transformations.…”

Evolution of Strategies in Paraconic Acids Synthesis

“…Pertusaria albescen , Trigonostemon howii found in Hainan island, China Punctelia microsticta collected on fruit trees at General Rodrıguez, Buenos Aires Province, Argentina, Punctelia albescens…”